In order the overcome the attenuation of red blood cells during iOCT imaging, we are proposing a novel approach involving CO2 injection to clear the erythrocytes. Currently CO2 is used as medium for digital subtraction angiography in patients with renal insufficiency and was first used in humans by Hawkins in 1982. The other alternative for angiography, iodinated contrast medium, is nephrotoxic and thus is avoided in these patients for fear of exacerbating the patient's acute or chronic problem. Another group where CO2 angiography is employed is history of a contrast allergy. Although this technique is usually used under these circumstances, Kerns et al reports conducting CO2 angiography in as high as 20% of their patients with abdominal and lower extremity studies.